Optical fibre cable incorporating a stack of fibre ribbon elements

Abstract

In an optical fibre cable, the transmission package comprises a stack (11) of ribbon fibre elements (110) secured within a metal tube (12) by an adhesive (13). The adhesive has a peel strength sufficiently low to permit separation of the individual ribbon from the stack, e.g. to effect jointing operations. Advantageously the adhesive is foamed by injection of a gas during cable manufacture.

We claim: 
     
       1. An optical fibre cable, including a stack of optical fibre ribbon elements enclosed in and supported by a tubular metal sheath, said stack of ribbon elements being secured to the sheath by an adhesive material selected from the group consisting of melt flow adhesives and ultraviolet curable adhesives, wherein there is substantially no overfeed of the stack of ribbon elements relative to the metal sheath, wherein said adhesive has sufficient tensile strength such that tensile forces applied in use to the cable are carried by the sheath whereby to protect the stack of ribbon elements from said forces, and wherein said adhesive has a peel strength sufficiently low as to allow separation of the ribbon elements from the sheath and separation of individual fibres from the ribbon elements whereby to access said fibres. 
     
     
       2. An optical fibre cable as claimed in claim 1, wherein said adhesive is foamed. 
     
     
       3. An optical fibre cable as claimed in claim 2, wherein said tubular sheath is enclosed within a further tube. 
     
     
       4. An optical fibre cable as claimed in claim 3, wherein said further tube comprises a metal tape formed into a cylinder and welded along the seam whereby to provide a hermetic seal. 
     
     
       5. An optical fibre cable as claimed in claim 4 and comprising a submarine cable. 
     
     
       6. An optical fibre cable as claimed in claim 5, wherein said tubular metal sheath is formed from a C-section metal extrusion closed into a tube around the stack of ribbon elements. 
     
     
       7. An optical fibre cable as claimed in claim 6 and further comprising a plurality of wire strength members disposed around said tubular sheath, a further metal tube enclosing the wire strength members, and an outer plastics sheath. 
     
     
       8. An optical fibre cable as claimed in claim 1, wherein said tubular sheath comprises an extruded metal tube. 
     
     
       9. An optical fibre cable as claimed in claim 8, wherein said tube is enclosed within a layer of electrically conductive wires. 
     
     
       10. An optical fibre cable as claimed in claim 9, and comprising an optical cable or groundwire.